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/*
* AdapterClass.oj
*
* An OpenJava example to support programming with the Adapter pattern.
*
* @author Michiaki Tatsubori
* @version %VERSION% %DATE%
* @see java.lang.Object
*
* COPYRIGHT 1999 by Michiaki Tatsubori, ALL RIGHTS RESERVED.
*/
package examples.adapter;
import java.lang.Object;
import openjava.mop.*;
import openjava.ptree.*;
import openjava.syntax.*;
/**
* The metaclass <code>AdapterClass</code> supports classes
* implementing an adapter role of the Adapter pattern.
* The target's methods with same signatures as the adaptee's are
* automatically implemented into the adapter class.
* <p>
* For example, the class <code>VectorStack</code>:
* <pre>
* public class VectorStack instantiates AdapterClass
* adapts Vector in v to Stack
* {
* Vector v;
* public VectorStack( Vector v ) {
* this.v = v;
* }
* public void push( Object o ) {
* v.addElement( o );
* }
* public Object pop() {
* return v.removeElementAt( v.size() - 1 );
* }
* }
* </pre>
* would be automatically implemented with the forwarding methods
* size(), isEmpty(), hashCode(), etc, which are found in both
* the class Vector(adaptee) and the class Stack(target).
* <p>
*
* @author Michiaki Tatsubori
* @version 1.0
* @since %SOFTWARE% 1.0
* @see java.lang.Object
*/
public class AdapterClass instantiates Metaclass extends OJClass
{
public static final String KEY_ADAPTS = "adapts";
/* overrides for translation */
public void translateDefinition() throws MOPException {
OJClass target = getTarget(), adaptee = getAdaptee();
if (target == null || adaptee == null) return;
/* implicit forwarding to the same signature's */
OJMethod[] adapteds = adaptee.getMethods( this );
for (int i = 0; i < adapteds.length; ++i) {
/* picks up the method with same signature */
OJMethod m;
try {
m = getTarget().getMethod( adapteds[i].getName(),
adapteds[i].getParameterTypes(),
this );
} catch ( NoSuchMemberException e ) { /* not match */ continue; }
/* generate a forwarding method with forwarded's name */
addMethod( makeForwardingMethod( m.getName(), m ) );
}
addInterface( getTarget() );
}
/**
* Generates a forwarding method with specified name.
*
* @param name generating method's name.
* @param forwarded method to which the generated method forwards.
* @return a generated forwarding method.
*/
private OJMethod makeForwardingMethod( String name, OJMethod forwarded )
throws MOPException
{
/* generates a new method without body */
OJMethod result = new OJMethod(
this,
forwarded.getModifiers().remove( OJModifier.ABSTRACT ),
forwarded.getReturnType(),
name,
forwarded.getParameterTypes(),
forwarded.getExceptionTypes(),
null
);
/* generates a method call and return statement */
ExpressionList params = result.getParameterVariables();
Expression expr = new MethodCall( getContainer(), name, params );
StatementList body = new StatementList();
if (forwarded.getReturnType() == OJSystem.VOID) {
body.add( new ExpressionStatement( expr ) );
body.add( new ReturnStatement() );
} else {
body.add( new ReturnStatement( expr ) );
}
result.setBody( body );
return result;
}
/* extended information */
private OJClass getAdaptee() throws MOPException {
ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS );
return OJClass.forName( suffix.get( 0 ).toString() );
}
private Variable getContainer() throws MOPException {
ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS );
return new Variable( suffix.get( 1 ).toString() );
}
private OJClass getTarget() throws MOPException {
ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS );
return OJClass.forName( suffix.get( 2 ).toString() );
}
/* override to extend syntax */
public static boolean isRegisteredKeyword( String keyword ) {
return keyword.equals( KEY_ADAPTS );
}
/* override to extend syntax */
public static SyntaxRule getDeclSuffixRule( String keyword ) {
if (keyword.equals( KEY_ADAPTS )) {
return new CompositeRule(
new TypeNameRule(),
new PrepPhraseRule( "in", new NameRule() ),
new PrepPhraseRule( "to", new TypeNameRule() ) );
}
return null;
}
}
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